1. Field of the Invention
The present invention relates to a battery comprising a cathode, an anode, and an electrolyte.
2. Description of the Related Art
In recent years, many portable electronic devices such as a combination VTR (video tape recorder), a mobile phone, and a mobile computer have been introduced. Downsizing and weight saving of these devices have been made. Along with these situations, as a portable power source for the electronic devices, a battery, particularly a secondary battery has been actively researched and developed. Specially, a lithium ion secondary battery provides a higher energy density compared to conventional lead batteries or nickel cadmium batteries do. Therefore, the lithium ion secondary battery is highly prospective.
Historically, a general lithium ion secondary battery has been the battery, wherein an electrolytic solution, the liquid electrolyte is used, and a metal container is used as an exterior member to prevent solution leak. However, when using the metal container for an exterior member, it is very hard to fabricate, for example, a sheet-type battery having a thin thickness and a large area, a card-type battery having a thin thickness and a small area, and a flexible battery having more freedom of shape.
Therefore, it has been considered to fabricate a battery by using a total solid electrolyte such as an inorganic solid electrolyte and an organic high molecular weight electrolyte, or a semisolid electrolyte such as a gelatinous electrolyte, wherein an electrolytic solution is held in a high molecular weight compound (for example, refer to Japanese Unexamined Patent Application Publication No. 2001-167797).
When using these solid electrolytes, there is no danger of leak, and a thickness can be fixed. In addition adhesion properties to the electrodes are excellent, so that contact with the electrodes can be maintained. Therefore, when using the solid electrolyte, there is no need to use the metal container for an exterior member, a dampproof laminated film and so on wherein a metal foil is sandwiched between a high molecular weight compound having heat anastomoses properties can be used, and a sealing structure of the battery can be easily realized by thermocompression and the like. Further, the dampproof laminated film and the like have a high strength and an excellent airtightness. In addition, they are light-weight, thin, and inexpensive compared to the metal container. Therefore, by using the dampproof laminated film and the like, light and thin batteries can be fabricated inexpensively.
The battery using the solid electrolyte is mainly used for notebook personal computers and mobile phones. Recently, the notebook personal computer mounts a high performance CPU (Central Processing Unit), and the mobile phone mounts a camera. Therefore, the notebook personal computer and the mobile phone with a camera need a large load current. Further, since the mobile phone with a camera is used in ski resorts and the like more excellent low temperature characteristics are required. Therefore, improvement in both high load characteristics and low temperature characteristics is required for batteries.